Microphones are transducers that convert, acoustic energy into electronic energy. Many transduction principles have been developed, including the piezoelectric microphone, the capacitive microphone and the contact microphone.
In the prior art, the majority of silicon microphones are based on the capacitive detection principle. These microphones are also called as the capacitive microphone or condenser microphone.
To improve the performance of a microphone such as sensitivity, a differential condenser may be used. A kind of condenser microphones includes condensers/capacitors among different diaphragms or back plate. For example, U.S. Pat. No. 8,860,154 discloses a CMOS compatible silicon differential condenser microphone, which is hereby incorporated herein by reference.
In the prior art, to provide a differential MEMS microphone, a three-layers structure is required. For example, in such a structure, the top layer is a diaphragm with a first electrode, the middle layer is a back plate with a center electrode, and the bottom layer is a diaphragm with a second electrode. The first and the second electrodes are used to output differential signals.
The Micro-Electro-Mechanical Systems, or MEMS, refers to a miniaturized mechanical and electro-mechanical member (i.e., devices and structures) that is made using the techniques of micro-fabrication. A MEMS microphone is a microphone which is based on MEMS technology.
Therefore, there is a demand in the art that a new condenser MEMS microphone shall be proposed to address at least one of the problems in the prior art.